The butterknife bolt handle makes sense if you carry your rifle frequently in a saddle scabbard. Otherwise for ease of rapid manipulation the round knob bolt handle is the overwhelming shoice. Walk down the firing line at a high power rifle match. All you will see on the bolt guns is round knobs, the bigger the better. The same goes for the length of the bolt handle shank, the longer the better.

Of course, aesthetics have to be taken into account as well, but keep in mind, the larger angle the bolt handle turns through (90 degrees for a Mauser and Mauser derived actions, 60 degrees for Weatherby type actions) the easier it will be to open the bolt against a reluctant cartridge case.

In his book The Bolt Action, Stuart Otteson offers the following comparison between Mauser type (in this case the 98 Mauser), and the Weatherby type actions (Weatherby Mark III)

Mauser Operating

Extraction set back .16 in.
leverage 8.5 to 1

Chambering cam forward .25 in.
leverage 8 to 1

Bolt rotation 90 degrees

Operating forces bolt lift 5 lb.
bolt turndown 6 lb.

Weatherby Operating

Extraction set back .07 in.
leverage 6.5 to 1
Chambering cam forward .08 in.
leverage 17.5 to 1

Bolt rotation 57 degrees

Operating forces bolt lift 12.5 lb.
bolt turndown 5 lb.

The Mauser action cams the spent cartridge case more than twice as far out as the Weatherby and cams the fresh cartridge more than three times as far in. The force required to open and close the bolt are virtually the same in the Mauser, for a total of 11 pounds, while the Weatherby requires a total of 17.5 pounds, due to the need of cocking the firing pin with only 2/3 or the camming travel of the Mauser.